and Cochoa, which inhabit Java, the
Himalayas, and Indo-China, all but the last extending south to Tenasserim,
but none of them occurring in Malacca, Sumatra, or Borneo. There are also
two species of birds--a trogon (_Harpactes oreskios_), and the Javanese
peacock (_Pavo muticus_), which inhabit only Java and the Indo-Chinese
countries, the former reaching Tenasserim and the latter Perak in the Malay
Peninsula.

Here, then, we find a series of remarkable similarities between Java and
the Asiatic continent, quite independent of the typical Malay
countries--Borneo, Sumatra, and the Malay Peninsula, which latter have
evidently formed one connected land, and thus appear to preclude any
independent union of Java and Siam.

The great difficulty in explaining these facts is, that all the required
changes of sea and land must have occurred within the period of existing
species of mammalia. Sumatra, Borneo, and Malacca have, as we have seen, a
great similarity as regards their species of mammals and birds, while Java,
though it differs from them in so curious a manner, has no greater degree
of speciality, since its species, when not Malayan, are almost all North
Indian or Siamese.

There is, however, one consideration which may help us over this
difficulty. It seems highly probable that in the equatorial regions species
have changed less rapidly than in the north temperate zone, on account of
the equality and stability of the equatorial climate. We have seen, in
Chapter X., how important an agent in producing extinction and modification
of species must have been the repeated changes from cold to warm, and from
warm to cold {385} conditions, with the migrations and crowding together
that must have been their necessary consequence. But in the lowlands, near
the equator, these changes would be very little if at all felt, and thus
one great cause of specific modification would be wanting. Let us now see
whether we can sketch out a series of not improbable changes which may have
brought about the existing relations of Java and Borneo to the continent.

_Past Geographical Changes of Java and Borneo._--Although Java and Sumatra
are mainly volcanic, they are by no means wholly so. Sumatra possesses in
its great mountain masses ancient crystalline rocks with much granite,
while there are extensive Tertiary deposits of Eocene age, overlying which
are numerous beds of coal now raised up many thousand feet above the
sea.[91] The volcanoe